Gas analyzer

ABSTRACT

A GAS ANALYZER IN WHICH AN ELONGATED GAS-TIGHT HOUSING IS SEPARATED INTO A BASE COMPARTMENT ANDS AN ELECTRODE COMPARTMENT BY A SHIELD. A SUPPORT AND A BURNER TIP EXTEND THROUGH THE SHIELD INTO THE ELECTRODE COMPARTMENT, THE SUPPORT CARRYING A COLLECTOR ELECTRODE MOUNTED COAXIALLY WITH THE BURNER TIP. AIR UNDER PRESSURE IS ADMITTED TO THE BASE COMPARTMENT AND PASSES THROUGH CONCENTRIC OPENINGS IN THE SHIELD SURROUNDING THE BURNER TIP AND SUPPORT, THEREBY PREVENTING COLUMN EFFUENTS AND PRODUCTS OF COMBUSTION FROM COATING THE ELECTRICAL INSULATORS, THUS PROVIDING LONG TROUBLE-FREE SERVICE. THE ELECTRICAL INSULATORS ARE DISPOSED WITHIN THE BASE COMPARTMENT.

g- 3, 1971 M. E..REINECKE 3,597,162

GAS ANALYZER Filed April 21, 1969 5 Sheets-Sheet 1 INVENTOR.

M. E. REINECKE A T TORNE VS Aug. 3, 1971 M. E. REINECKE GAS ANALYZER 3 Sheets-Sheet 2 Filed April 21 1969 INVENTOK.

M.E. REINECKE A TTORNEVS Aug. 3, 1971 M. E. REINECKE GAS ANALYZER 5 Sheets-Sheet 5 Filed April 21, 1969 FIG.

A 7 TORNE VS United States Patent 70" 3,597,162 GAS ANALYZER Marvin E. Reinecke, Bartlesville, Okla, assignor to Phillips Petroleum Company Filed Apr. 21, 1969, Ser. No. 817,665 Int. Cl. Gtlln 31/12 US. Cl. 23254 6 Claims ABSTRACT OF THE DISCLOSURE A gas analyzer in which an elongated gas-tight housing is separated into a base compartment and an electrode compartment by a shield. A support and a burner tip extend through the shield into the electrode compartment, the support carrying a collector electrode mounted coaxially with the burner tip. Air under pressure is admitted to the base compartment and passes through concentric openings in the shield surrounding the burner tip and support, thereby preventing column eflluents and products of combustion from coating the electrical insulators, thus providing long trouble-free service. The electrical insulators are disposed within the base compartment.

BACKGROUND OF THE INVENTION This invention relates to a gas analyzer.

Various types of gas analyzers are known wherein a combustible mixture, such as a carrier gas and hydrogen, is passed through a burner tip and ignited. A collector electrode is disposed coaxially with the burner tip, and an elec trical potential dilference is established between the burner tip and collector electrode. When the gas contains ions, such as produced by hydrocarbons, electricity is conducted between the collector electrode and burner tip which can be measured by an electrometer. The ion currents measured are extremely small and a high impedance output is required. The leakage resistance of the insulators must be very high, of the order of l to 1X 10 ohms and remain at that value as the analysis proceeds. Products of the flame have a tendency to coat the insulator, causing surface leakage or a lowering of the resistance value. This problem is accentuated Where greater sensitivity is obtained by utilizing a high voltage bias on the burner tip, say of the order of 1200 volts. Further require ments are that the unit of gas-tight rugged construction, and that precautions be taken to avoid flame passing through the vent of the analyzer.

BRIEF STATEMENT OF THE INVENTION I overcome these problems by forming an elongated gas-tight housing having a metal base which is separated by a shield into a base compartment and an electrode compartment. A burner tip protrudes from the base through the shield into the electrode compartment. The base further carries a conductive support member which extends through the shield and into the electrode compartment, the support being spaced from the burner tip. The end of the conductive support member carries a collector electrode which is disposed coaxially with the burner tip. The electrical insulators are mounted Within the base compartment.

The gas to be analyzed and hydrogen are fed through a bore in the base to the burner tip. An electrometer and a current source are connected in circuit with the burner tip and the conductive member.

According to the invention, air is passed into the base compartment and passes through the shield to the electrode compartment. The shield is constructed and arranged to provide small orifices surrounding the burner tip and the support member, and the air is maintained under sufficient pressure to prevent any backfiow of gas from the Patented Aug. 3, 1971 ice electrode compartment to the base compartment. The clean air sweeping through the orifices prevents the deposit of condensation products or dirt on the burner tip, collector electrode and support, thus providing long troublefree service. Moreover, the insulator, being mounted in a separate compartment, is completely shielded from contact with the combustion products.

At the end of the electrode compartment remote from the shield is provided a temperature sensor, such as a thermistor, and an igniting device. This permits the temperature to be measured and provides a convenient means for starting the flame. The gases leaving the analyzer pass through a vent fitted with a screen which acts as a flame arrestor so that, if an explosion occurs during ignition, it is confined to the interior of the instrument.

DETAILED DESCRIPTION OF THE INVENTION Various other objects, advantages and features of the invention will become apparent from the detailed description taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a vertical, sectional view of a gas analyzer constructed in accordance with the invention;

FIG. 2 is a vertical, sectional view of a modified form of gas analyzer; and

FIG. 3 is a vertical, sectional view taken along the lines 33 of FIG. 2 looking in the direction of the arrows.

Referring now to the drawing in detail, an elongated gas-tight housing is provided by a metal base 10 having an elongated cap 11 threaded thereto, the assembly being sealed by an O-ring 12. As shown, the cap is of generally cylindrical construction and the upper end thereof has a reduced section 13 constituting a vent for the products of combustion, as will hereinafter become apparent.

A shield 14 formed, for example, from Teflon, is mounted transversely of the housing and divides the interior thereof into a base compartment 15 and an electrode compartment 16. A metal burner tip 17 is mounted on the base 10 by a ferrule 18 of high resistance insulating material which is clamped gas-tight within a threaded bore in the base by a nut 19. The burner tip communicates with a bore 20 in the base 10 through which combustible gas to be analyzed and hydrogen are introduced. The bore 20 has an outlet, not shown, in the side of the base 10. The shield 14 is provided with an opening or orifice 21 slightly larger than the burner tip so that air can pass from the base compartment 15 to the electrode compartment 16 in the manner hereinafter described.

An electrical connection is made to the burner tip 17 by a spring clip 22 attached to a jack 23 which, in turn, is connected to a high voltage feed-through conductor 24 secured to the base by a clamp nut 25. A sleeve 26 of insulating material of very high resistance, of the order of 1x10 ohms, insulates the conductor 24 from the base. As previously noted, the ferrule 18 is likewise formed of insulating material of high resistance so that the burner tip is electrically insulated from the base. The insulating materials can be plastics, if desired, such as Teflon.

An elongated support member 2,7 of conductive material is spaced from the burner tip and extends from the base 10 through the shield 14 into the electrode compartment 16. This member carries a generally cylindrical collector electrode 28 which is disposed coaxially with the burner tip. To this end, the member '27 comprises an offset rod 30 carrying the collector electrode and connected, in turn, to a support rod 31 which is attached to an electrical plug-in connector 32'. The connector has a metal sleeve sealed by an O-ring 33 and a jack .3 4 which is electrically connected to the rod 31. The connector 32 has an insulating washer 32a and an insulating sleeve 32b of high resistance. Thus, the jack 34 and its feed-through conductor asav, 162

34a are electrically insulated from the base 10, which is grounded.

The shield 14 has an orifice 35 therein of slightly larger diameter than that of the rod 31 to permit air to pass therethrough from the base compartment to the electrode compartment in the manner hereinafter described. The air is supplied to the base compartment through a bore 36.

A temperature sensing device, such as a thermistor 37 is disposed at the upper end of the electrode compartment, the thermistor being carried by a suitable support rod 38 which is insulated and sealed by a suitable clamp 39. An igniter 40 is mounted at the upper end of the electrode compartment, and can conveniently consist of a coil of resistance wire heated by a current source, not shown.

The reduced upper end 13 of the electrode chamber is threaded, as indicated at 41, to receive a conduit for carrying away the products of combustion. A metal screen, not shown, is inserted within the conduit and serves to confine any explosion which may arise during ignition of the gases to the electrode compartment.

OPERATION In operation, the jack 34 and conductor 24 are connected in circuit with an electrometer and a high potential source. The gas to be analyzed is passed through the bore to the burner tip 17 and combustion is initiated by operation of the igniter 40. Where the gas contains no ions, there is no current flow between the burner tip and electrode and, hence, there is no output to the electrometer. This occurs, for example, when a mixture of carrier gas and hydrogen from a chromatographic analyzer is fed to the burner tip. When hydrocarbons are present in the gas to be analyzed, ionization occurs, and current is conducted between the burner tip 17 and electrode 28, thus producing an output signal at the electrometer. Due to the high potential, the presence of minute quantities of hydrocarbons, i.e., a few parts per million, can be readily detected and measured.

In accordance with the invention, air is introduced through the bore 36 into the base compartment at suflicient pressure to prevent back dilfusion of the gases from the electrode chamber 16. This air serves to support combustion of the hydrogen, and also purges the surfaces of the parts within the electrode chamber to keep them clean. In particular, the air passing through the orifice 35 cleans the rods 30, 31, and the air passing through the orifice 2,1 cleans the burner tip 17 and electrode 28.

It will be observed that the insulators 18, 26, 32a and 32b are mounted Wholly within the base compartment and separated from the electrode compartment by the shield 14. Thus, no condensation or other products of combustion can collect on the insulators and reduce the necessarily high resistance thereof. As noted, the orifices 21, 35 are sufiiciently small that there can be no diffusion of gases from the electrode compartment 16- back into the base compartment 15. Due to the combination of physical separation between the compartments and the provisions of the orifices 21, 35 long trouble-free operation of the analyzer is readily obtained.

The analyzer has been successfully utilized over extended periods of time to measure concentrations of the order of 2 parts per million, full scale, of cyclopentadiene in isoprene. In another application, concentrations of the order of 3 parts per million of acetylene in ethylene were readily measured.

MODIFIED FORM OF THE INVENTION In FIGS. 2 and 3 I have shown a modified form of gas analyzer constructed in accordance with the invention.

This differs from the analyzer shown in FIG. 1 principally in the insulation details. In this embodiment, a metal base 50, FIGS. 2 and 3, has an elongated cap 51 threaded thereto which encloses a smaller elongated metal cap 52 carried within a flanged portion 53 of the base 50 and abutting a Teflon shield 54. As in FIG. 1, the shield divides the analyzer into a base compartment 55 and an electrode compartment 56.

The cap 52 carries a thermistor S7 and igniter 58, FIG. 2, similar to those described in connection with FIG. 1. The electrical connections to the thermistor and igniter are made by a feed-through assembly 59, FIG. 3, in the base 58/.

A burner tip 60 is supported by a ferrule 61 of insulating material which is secured within a threaded recess in the base 50 by a clamp nut 62. The burner tip is connected to a bore 63 in the base through which the gas to be analyzed and hydrogen are introduced. The burner tip protrudes through an orifice 64 in the shield 54 and extends into the electrode compartment 56.

As shown most clearly in FIG. 2, an electrical connection is made to the burner tip 69 by a jack 65 extending through a vertical bore in the base and secured therein by a clamp nut 66. The jack is insulated from the base by a sleeve 67 of insulating material of very high resistance. A feed-through conductor 68 extends through the sleeve 67 and is electrically connected to the burner tip 60 by a spring clip 69.

A jack 70 and clamp nut 71, of similar construction to the jack 65 and clamp nut 66, are secured within a vertical bore in the base 50 which is spaced from the jack 65. An insulating sleeve 72 has a conductor rod 73 disposed therewithin which is mechanically and electrically connected to a rod 74. The rod 74 extends from the base compartment 55 through an orifice 75 in the shield 54 into the electrode compartment 56. It carries an ofiset rod 76 which, in turn, supports a collector electrode 77 in coaxial relation with the burner tip 60.

The operation of the modified form of analyzer is similar to that described in connection with FIG. 1. The gas to be analyzed and hydrogen are passed through the bore 63, FIG. 3, to the burner tip 60 and ignited through actuation of the device 58. An electrometer and high voltage source are connected in circuit with the jacks 70, 65 so that an electrical output is produced when the gas contains even a minute quantity of ionizable components.

Air is introduced to the base compartment 55 through a bore, not shown, and this air passes through the orifices 75, FIG. 2, and 64, FIG. 3, to support combustion of the sample gas and clean the rods 74, 76 together with the collector electrode 77 and burner tip 60. The products of combustion leave the cap 51 through bore 78, FIG. 3, which communicates with a conduit carrying a flame arrester.

As in the anlyzer of FIG. 1, all the insulating material, i.e., the sleeves 67 and 72, FIG. 2, are mounted Within the base compartment 55 wherein they are physically separated from the electrode compartment by the shield 54. The air is introduced at a suflicient rate that no back diffusion of combustion products can occur from the electrode compartment 56 to the base compartment 55.

It will be apparent that I have achieved the objects of the invention in providing a gas analyzer of rugged explosion-proof construction wherein the insulation capabilities are etfectively preserved over long periods of time, and the parts are kept free of condensation products of the gas being analyzed. The a-nlyzer further contains an integral igniter, and is provided with a flame arrestor to effectively confine any explosion resulting from ignition of the gas to the interior of the electrode chamber.

Other variations and modifications of this invention will be apparent to those skilled in the art without depart ing from the spirit and scope of the invention.

I claim:

1. A gas analyzer comprising, in combination, an elongated gastight housing having a base, an elongated burner tip of conductive material mounted on said base and protruding into said housing, an elongated support of conductive material protruding from said base and spaced from said burner tip, a generally cylindrical collector electrode mounted on said support and disposed coaxially with said burner tip, means for supplying a combustible gas to said burner tip, means for making electrical connections to said burner tip and said electrode, a shield extending transversely of said housing between the base and electrode, thereby dividing said housing into a base compartment and an electrode compartment, said shield being constructed and arranged to provide an orifice surrounding said burner tip and an orifice surrounding said elongated support, and means for passing air under pressure to said base compartment, whereby the air passes through said orifices into the electrode compartment and prevents deposit of combustion products on said burner tip and said support.

2. The analyzer of claim 1 wherein insulating members separate said means for making electrical connections to the burner tip and electrode, and said burner tip from the base, said insulating members being mounted within said base compartment.

3. In the gas analyzer of claim 1, a temperature sensing device and an ing-nition device mounted within the electrode compartment and arranged to ignite gases passing through the burner tip and measure the temperature thereof.

4. The gas analyzer of claim 1 comprising a ferrule of insulating material secured to said base within the base compartment, said burner tip being mounted within 6 mentioned means includes a jack mounted within a bore in said base, a sleeve of insulating material separating said jack from said base, said jack being electrically connected to said elongated support, a feedthrough conductor extending through another bore in said base, a sleeve of insulating material insulating said feedthrough conductor from said base, and a spring clip of conductive material connecting said feedthrough conductor with said burner tip.

6. The gas analyzer of claim 4 having a ferrule of insulating material secured to said base and carrying said burner tip, said burner tip communicating with a bore in said base, a pair of electrical feedthrough conductors disposed within spaced bores in said base, sleeves insulating the respective conductors from said base, jacks electrically connected to the feedthrough conductors, and a clip of conductive material connecting one of said feedthrough conductors to said burner tip, the other feedthrough conductor being connected to said elongated support.

References Cited UNITED STATES PATENTS 7/1969 Jentzsch et a1. 23-254E 1/1970 Clardy et al. 23254E U.S. Cl. X.R. 23-232 

